1. Field of the Invention
The present invention relates to novel powder coating compositions for forming films having enhanced mechanical properties. This invention also relates to a process of making the powder coatings. More specifically, the invention relates to novel powder coating compositions containing novel aliphatic hyperbranched polymers, which function either as polymeric crosslinkers or as flow and leveling agents.
2. Description of the Prior Art
Powder coating compositions containing a wide variety of polymeric binders are very well-known. Some of the known powder coatings, particularly, the ones which may relate to the present invention are briefly described herein below. A number of different types of hyperbranched polymers have also been reported in the prior art, some of which are briefly described below.
However, there is a need for improved powder coating formulations having enhanced mechanical properties that are low temperature or photo-curable and can be applied onto non-metallic surfaces. For example, the powder coatings having low melt viscosities are extremely desirable such that they can be readily applied onto a wide variety of surfaces to form thin and smooth films without the formation of the undesirable "orange peel". Another property sought after is low glass transition (T.sub.g) polymeric binder (base resin) containing powder coatings, which cures to high glass transition compositions after application. Even yet an important property sought after is powder coating compositions containing polymeric binders, which can be cured either at lower temperatures or using actinic sources such that they can be applied onto non-metallic surfaces such as wood and plastic. Improved chemical and solvent resistance properties are also highly desirable. None of the prior art references described below feature all of these desirable attributes.
Therefore, it is an objective of this invention to provide novel powder coatings that exhibit properties as described hereinabove. These compositions contain novel hyperbranched polymers. The hyperbranched polymers of this invention can be used either as polymeric binders (i.e., base resin), crosslinkers, adhesion promoters, as well as flow and leveling agents depending upon their chemical structure. This invention also provides a process for making these novel hyperbranched polymers. The hyperbranched polymers of this invention are also found to possess adhesive properties.